vcb

Hi,
I have a pair of Holleys 4779 and was thinking on putting it in.
Has anyone done it? Does it add any gain.
What about MPG? How would it effect it?
I will also put a MSD 6al-2 system to make all fuel is burned.
I was about to add a 671 but decided to keep it under the hood.
thx
v

73StreetRace

I think two 4-barrel 750 cfm holley carbs is a bit too much for a simple 350...
Except the great look and the "Wow effect", that's a lot of tuning to make them work as well as a single carb.
A good cam, intake manifold and heads with a stock quadrajet carb would certainly make much more power...
With a single 750 cfm, you can already rev your 350 beyond 7000RPM...
A 350 engine turning 6,000 RPM at 100 percent VE only needs 607.6 cfm ! Too big carb is generally worse than too small.
Driveability can also be disastrous, so if you want to keep the car streetable... But that's just my opinion...
Here are some general recommendations :

All things being equal, a bigger engine requires a larger carb. But for any given engine size:

• Higher rpm requires a bigger carb

• Higher horsepower requires a bigger carb

• Higher compression ratios require a bigger carb

• More distributor mechanical advance requires a bigger carb

• A manual-trans car can use a larger carb than an automatic-trans car

• Steeper (higher numerical) rearend gears tolerate a bigger carb

• Lighter cars can use a bigger carb

• Heavy cars need a smaller carb

• Too large a cam for the application requires a smaller carb

• With an automatic-trans car, too low a torque-converter stall-speed for the application requires a smaller carb

• Mild (lower numerical) rearend gears require a smaller carb

• Low compression requires a smaller carb

About mpg, with two double pumpers, it WILL be affected...

lars

You can certainly install 2 750s on a dual quad on a 350 engine and make it run. No problem. But the car won't perform well unless this is a heavily modified engine intended for extreme high rpm usage.

I just finished installing and testing a Pontiac 389 that the customer wanted dual quad 750s on. Idle and low-speed drivability is normal, and throttle response at light throttle is also normal provided progressive linkage is used to allow the engine to run only on one carb at low speed (with idle speed split between the two carbs). Torque, power, and high-rpm throttle response is down significantly over what it would normally be with a single, properly tuned 750 carb on a good intake.

If your objective is just looks, the dual 4 can look very cool. If you want to go fast, set up and tune a single 4-barrel of the right size on a good intake.

Lars

MotorHead

Please, no one use "The Formula"

Yeah you could make it work and it would look cool too. You need some fairly good tuning skills, a pair of 4777's and a beefed up 355ci would be better but if it's for show, go for it

lars

Wayne -
Unfortunately, you and I are in the minority when it comes to realizing that "The Formula" is nonsense to a good tuner.

Lars

MotorHead

I literally cringe when I see it

l88rocket

I would say a pair of 500's would be the max for a mild 350. i would use a short eldbrock intake thou not a tall tunnel ram

MotorHead

I think he already has the 750's so I would say it's 1500cfm if he's gonna do it. I think Edelbrock makes a low profile 2x4 intake

SanDiegoPaul

What compression ratio you thinking of using? You ~can~ burn all that fuel-but as Lars says it ain't going to happen w/out lotsa mods.

Rmorgan&11

Seen 2 -780's on a 283 before ,,but it was " slightly " modified...

midyearvette

..i wish these manufacturers would stop printing that kind of crap, especially for the un informed enthusiast who believes what is in print is gospel....im assuming the op is talking a crossram as i dont think two holleys will fit a 350 in line bwdik??.....happy fathers day to all...

MotorHead

I haven't obviously looked into it for while but I though there was one manifold that you could fit them inline, that is the way I would want to install them, pretty sure you can do the sideways

SanDiegoPaul

That was ME!

'56 Bel Air ... 283 punched out to 292 (.060") with a solid cam, Muncie 4-speed and an 8500 RPM Redline. I was running 12:1 compression and pump gas ... pushed that lil' ol' Bel Air thru the traps in 12.5 seconds. Low torque motor, so the original pumpkin style rear end held up just fine - though I put a 4:56 posi in it.

Everyone used to go tap,tap,tap around the body looking for 'glass body panels. It was all stock-bodied ... and Quick!

Ahh, the good ol' days.

Rmorgan&11

Your Close !
the guy I know ..John Gawlik ...ran a '51 Ford pickup with 283 , Tunnelram , 780's, probably closer to 14:1 compression , BW Super T-10 & 5:88 cogs in the rear....wouldn't shift till the valves floated ...LOL

Rmorgan&11

But back to his original question , of course you can run them on a 350
..Jegs,Summit, Herbert, and every other mail order catalouge and their dog sells the Edelbrock setup...so it has to work !

leadfoot4

Tuning and drivability issues aside, I would think you'd need at least a big block hood, to clear 2 4bbl. carbs and any kind of air cleaners.

midyearvette

like i said.bwdik??......

Ironcross

GM use quads on Chevys from the 1956 265 ci engines through the 1961 283`s with both solid lifter and hydraulic cam engines in most of the years in that period....His carb selection may be too much for most combinations,,,But yes dual quads, why not....just do it right'

MotorHead

isduwym

leadfoot4

Very true. However, weren't most of the 4bbls. back then something like 475-525 CFM, hence the need at WOT for 2 of them??